Mitch, the F25 is indeed an excellent sub, and will work quite well with the ET LFT-8b. I have a pair of F15HP’s (DIY version---I made my own 4cu.ft. enclosures), which have a single 15 woofer to the F25’s dual 15’s. Same sq, but the F25 has greater maximum spl. Both the F15 and F25 are being used successfully with magnetic-planar (mostly Magneplanars), ESL, and ribbon loudspeakers.
For reference, I am a former owner of Infinity RS-1b’s, and I consider the ET LFT-8b a superior loudspeaker. However, the LFT-8’s single 8" woofer is no match for the RS-1b’s servo-feedback woofer column, with it’s 6-8" woofers. Any of the Rythmik servo-feedback subs will be a great partner for the LFT-8 (used in place of the ET’s woofer), creating a very full-range, high-output hybrid. But for the ultimate version of such a design, there is an even better sub for use with dipole speakers, one also available from Rythmik’s Brian Ding, in a collaborative effort with Danny Richie of GR Research: their Servo-Feedback OB/Dipole Subwoofer, the only such design in the world! You can read about it on the GR Research AudioCircle Forum---there is too much to it for me to post here.
$1500 for a pair of the sub kits (a pair of 12" woofers with the Rythmik servo-feedback plate amp per side), another $500 for a pair of the H-frames they are installed in. $2500 for the ET LFT-8b’s, $2000 for the subs (plus the cost to finish the H-frames)---$4500 for performance far exceeding what you expect at that price point imo. The ultimate magnetic-planar/dynamic sub hybrid! Imagine---a dipole planar speaker with a dipole/OB sub---a perfect pairing!! I can say all this not just hypothetically and from theory, but from practice---this hybrid is my creation! As far as I know, I am the only ET LFT-8b/OB-Dipole Sub owner in the world. But the OB/Dipole Sub s being used with lots of other high-performance speakers, mostly ribbons. Ric Schultz of EVS has designed and is selling such a design, using the Rythmik/GR Research OB/Dipole Sub.
